1. Field
An aspect of embodiments of the present invention relates to a secondary battery.
2. Description of the Related Art
In general, unlike primary batteries which are not designed to be recharged, secondary batteries refer to batteries which are designed to be recharged. The secondary batteries are widely used in fields of electronic devices, such as cellular phones, notebook computers, and camcorders.
Among various kinds of secondary batteries, lithium secondary batteries are widely used due to their relatively high operating voltage and energy density per unit weight. The lithium secondary batteries are manufactured in various shapes, and representative shapes thereof may include a cylindrical shape, a can shape, a pouch shape, and the like.
Gas is generated by a reaction with an active material or electrolyte inside a secondary battery. When a space (e.g., a bubble) is formed inside the secondary battery by the gas, there is formed a region in which the function of the active material is lost or the movement of lithium ions in the electrolyte is interrupted, thereby shortening the lifespan of the secondary battery. When the generated gas accumulates, the internal pressure of the secondary battery increases and the secondary battery swells, and therefore, a risk of explosion may exist.
Accordingly, it is desirable to prevent the function of the active material from being lost by exhausting the gas generated inside the secondary battery to outside of the secondary battery and remove bubbles generated in the electrolyte. To this end, a vent portion may be formed so that a portion of a case is fractured when the internal pressure of the secondary battery increases.